It is known in the field of seismic exploration to effect remote control, from a central command and recording system (control station), of data acquisition devices, each of which is provided for collecting data signals which are received, for example, by one or more signal receivers, and for processing and recording these data signals. Such a method is helpful, for example, in providing to remote acquisition devices a reference time (TB) when a seismic signal generator is triggered, so that these devices can begin to collect the data signals provided by seismic sensors or groups of seismic sensors distributed along a seismic profile to be explored in response to the echoes from shocks communicated to the ground by the seismic signal generator on the various underground reflective layers, before these data signal are transmitted to the central command and recording system, usually by radio. Such an acquisition device is described in published French Patent Application No. 2,511,772.
In order to avoid any delay in the transmission of the signal which defines this reference time (TB) and in order to ensure the initialization of the acquisition devices before the arrival of the first echoes, it is possible to use, for example, a high-speed transmission channel to transmit this signal to the various acquisition devices. This transmission channel can be, for example, the same wide passband radio channel which is provided for transmitting the data signals collected by the acquisition devices to the central command and recording system. However, in this case, when the signal which indicates the reference time has been transmitted and received by the radio transmission-reception devices associated with the various data acquisition devices, it is necessary to perform fast switching between the transmitting and receiving sections of these devices, as well as between the corresponding sections of the transmitter-receiver associated with the central command and recording system in order to ensure that the seismic data signals which are collected can be transmitted and received immediately at the respective ends of the transmission channel. Unfortunately, this procedure has drawbacks due to the fact that the fast switching of the transmitters and receivers is not easy to accomplish.
On the other hand, the use of a second wide passband radio channel to transmit the signal which represents the reference time has not always been possible due to the restrictions on the availability of such communication channels imposed by the regulations regarding radio transmission. Less restrictions are imposed on the availability of narrow passband transmission channels; however, such transmission channels are known to operate at a relatively-slow transmission speed which would not be suitable in conventional systems to ensure initialization of the acquisition devices before the arrival of the first echoes.